Rectifier and modulator



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wQ F J. P. SCHAFER RECTIFIER AND MODULATOR Origirggl Filed Dec. 192s Nov. 8, 192 7.

mvemon- J/m F? Sc/vafer by A77)? Patented Nov. '8, 1 927.

, UNITED STATES PATENT OFFICE} I JOHN PETER SCHAFER, OF RICHMOND HILL, NEW YORK, ASSIGNOB TO WESTERN ELECTRIC COMPANY, INCORPORATED, 015 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

RECTIFIER AND MODULATOR.

Application filed December 19, 1928, Serial. No. 681,589. Renewed April 20, 1927.

This invention relates to improvements for rectifiers and modulators.

In systems of signaling by electrlc waves and particularly in radiant energy systems employing space discharge tubes or various purposes, it has been foundpossible to utilize polyphase alternating current as sources of space current, filament heatlng current, grid potentials and the like. To make possible the use of this current, it is rectified and means is then provided to eliminate harmonic or other variations or ripples that ocour in the rectified current.

This invention provides means in electric wave signaling systems for utilizing polyphase alternating current as the source of energy for vacuum tube amplifiers, rectlfiers, modulators and oscillators. Improved means also is provided for eliminating the harmonic variations or ripples produced in rectified polyphase current.

An object of this invention is to eliminate the ripples resulting when polyphase alter nating current is rectified, whereby the rectified current may be utilized as the source of space current for a space discharge modulator.

Another object of the invention is to apply to the control electrodesof a space discharge modulator-rectifier potentials varying In accordance with ripples in the :rectified current, whereby the ripples are greatly reduced or substantially eliminated.

A further object of the invention is tosupply energy to a space discharge oscillator from a source of polyphase alternating cur rent.

Another object of the invention is to heat the filaments of tubes of electron discharge tube amplifiers, rectifiers, and oscillators from a source of polyphase alternating current.

A feature of the invention is an arrangement of condensers and resistances to eliminate harmonic variations or ripples in the current from a polyphase rectifier.

Another feature of the invention relates to means, coupled between the input and output circuits of a rectifier-modulator, for impressing potentials on control electrodes thereof to eliminate ripples in the rectified current therefrom.

A further feature concerns means in the space path of a space discharge oscillator for suppressing ripples in the current therein.

In carrying out this invention, it may be embodied in a radiant energy signal transmitting system comprising a source of signals, such as a microphone, and a s ace discharge amplifier therefor. A recti er-modulator is arranged to be controlled by the source of signals and to supply rectified polyphase current to a space discharge os-' cillator. A circuit containing a reslstance and condensers is connected between the input and output circuits of the rectifier-modulator to impress ripple potentials on the control electrodes thereof for suppressing the ripples in the rectified current. An antiresonant circuit is connected in the current supply circuit of the oscillator to suppress ripples remaining therein.

In the drawing, the figure shows a radio transmission system employing a rectifiermodulator connected to a polyphase source of current, and means for suppressing ripples in the rectified current.

The system shown in the figure com rises a rectifier-modulator 30 controlled y a source of signals 10 for supplying energy to a space discharge oscillator arranged to transmit signal modulated energy to an antenna 75.

Signal source 10, which is here indicated as a microphone transmitter, is connected in series with battery 11 to the primary winding 130:5 transformer 14.

A speech frequency amplifier 20 is interposed between signal source 10 and rectifiermodulator 30 toproduce amplified signal. current variations. This amplifier comprises a space discharge tube 21 having three electrodes. The input circuit of this amplifier, which is connected between two of these electrodes, comprises the secondary winding of transformer 14, shunted by resistance 9, in series with a condenser 16. The resistance 9 acts as a stabilizing impedance.

The output circuitof amphfier 20' connects between the filament and plate of tube 21 and includes the primary wlnding 22 oftransformer 23. This output circuit is supplied with energy from the rectifier 30 and may be traced as follows: plate of tube 21, winding 22, choke coil 24, through the space paths of tubes 31, 32, 33, 34, 35 and 36 in three-electrode space discharge tu es 31, 32,-

to block direct current.

The rectifier-modulator com rises the 33, 34, and:36. The plates of tubes 31 and 32 connect to the terminals of winding 37 of transformer 38 having a primary winding 39. The plates of tubes 33 and 34, 35, and 36, connect to, respective terminals of secondaries 40 and 43 of transformers 41 'cuits of the tubes.

and 44 having respective primaries 42 and 45. The primary windings 39, 42 and 45 are star connected to a source of three-phase alternating current. The divided portions of primary windings 37,40 and 43 are'shunted by condensers 46.

The filaments of each air of rectifier tubes are connected mutua ly in parallel to divided resistances 47 48 and 49, respectlvely. Adjustable series resistances 50, 51 and 52 are connected, respectively, between divided resistances 47, 48'and 49 and the corresponding filaments to ermit balancing of the impedance of the lamentlate cir- Resistances 4 48 and 49 are in shunt, respectively, to secondary windings 54, 55 and 56 of transformers 57, 58 and 59. These transformers, having their primary windings connected in shunt to respective primaries of transformers 38, 41 and 44, supply heating current to the filaments of the rectifier tubes.

- A common input circuit is connected between the grids and filaments of the tubes of rectifier 30 and comprises secondary winding 29 of transformer 23 shunted by resistance 17, a portion of resistance 18 comprises divided paths, one passing by way of the space path of tube 21, the other by way of the space path of tube 71 of oscillator 70. The circuit through tube 21 may be traced as follows: from the midpoint of transformers 37, 40 and 43, through resistance 25, divided resistance 26, filament and ed across filament and plate electrodes and a-iresonant circuit 72 connected between the input and output circuits.

The in ut circuit comprises a high freuency c oke coil 73, arranged to prevent t e passage of oscillatory currents. In series with 73 is a resistance 74 for regulatin the flow of current leaking from the gri The output circuit of the tube may be traced as follows :-plate oftube 71 high frequency choke coil 76, divided resistances '47, 48 and 49, resistances 50, 51 and 52 in parallel, to the filaments and plates of the tubes of rectifier 30 in parallel, windings 37 40 and 43 in parallel to the resonant circuit 77-78, divided resistance 79 to the filament of tube 71. This circuit constitutes the second path of the output circuit of the rectifier as mentioned above. Resonant circuit 72 comprises an inductance 60 having its midpoi'ntconnected to the filament of tube 71 by way of resistance 79. It also comprises a variable condenser 61 connected across inductance 60.

The resonant circuit 72 connects between the filament and plate of tube 71 in series with a resistance 53 and a condenser 66. Resistance 53 serves to prevent arasitic oscillations from being establishe in the oscillator. Condenser 66 prevents the passage of direct current through the resonant circuit.

Antenna 75 is connected to ound in series with inductance 63 which is coupled to inductance 60.

The filament of tube 71 is heated by means of transformer 65 having its primary winding connected to the terminals of primary windin 45 and its secondary winding connected 1n parallel to the resistance 79 and i the filament of tube 71.

The resistance 18 has its terminals connected across the output circuit of rectifiermodulator 30. It is provided with a variable contact 67 connected intermediate to variable condensers 19 and 68 in series to the terminal of this resistance. This arrangement of condensers 19 and 68 and resistance 18 is pro.-

vided for impressing ripple potentials upon the grids of tubes 31, 32, 33, 34, 35 and 36 to suppress ripple variations in the currents rectified by these tubes.

Considering now the operation of the system, microphone 10 upon being actuated by sound waves of speech or other form, produces variations of current in the primary 13. Corresponding variations in the potential induced in the secondary 15 are transmitted to the grid of tube 21, and, there are produced in the output circuit of the amplifier 20 amplified current variations corresponding to signals. These current variations occurring in the primary winding 22 cause similar variations of electromotive force in the secondary winding 29 which are impressed upon the grids of the rectifier tubes. There result, therefore, corres 0nding current variations in the output circuit of the rectifier that are transmitted to the oscillator 7 0 and serve to modulate or vary the amplitude of oscillations generated therein in a manner well understood. Signal modulated energy is accordingly transmitted from the oscillator to the antenna from which it is radiated.

Current from the rectifier 30 may contain harmonic variations or ripples which are detrimental to the best operation of the system. Means is therefore rovided to eliminate these ripples. Recti ed current passes through resistance 18. The ripple component of this current, however, passes through condensers 68 and 19 in series. Condenser 19 and the portion of resistance 18 shunted thereby are common to the input and output circuits of the rectifier tubes. Thus, the component of ripple potential across the condenser 19 is im ressed upon the grids of the rectifier tubes in such manner as to oppose the variations of ripple frequenc in the rectified currents. The value of't e ripple potentials impressed on the grids of these tubes may be adjusted by varying condensers 68 and 19 and by adjusting contact 67 of resistance 18 so as to have a value whereby the ripple variations of current are substantially eliminated.

Additional means is provided for preventing ripple variations in the rectified current transmitted to the oscillator 70. This means comprises resonant circuit 77-78 which may be tuned to any desired frequency but preferably to the frequency of ripples, by adjusting variable inductance 77. It thereby ofiers relatively high impedance to currents of ripple frequency flowing in the output circuit.

Condenser 16 in the input circuit of tube 21 is shunted about -a portion of resistance 25 to by-pass signal frequency currents. Resistance 25 serves as a means for producing a desired average potential upon the grid of tube 21. Variable resistances 50, 51 and 52 are provided to enable the amount of heating current supplied to the corresponding filaments to be adjusted. Condensers 46 in shunt to'the windings 37, 40 and 43 are provided to supply low impedance paths for currents of signal frequency. Choke coils 73 and 76 serve to prevent the passage of oscillatory currents through the space paths of rectifier-modulator 30.

Although this invention has been illustrated and described in accordance with a particular embodiment, it is apparent that 41 and 44 may have their windings connected in many other well known arrangements and antenna 75 may represent any signal conductor such as a wire transmission line.

\Vhat is claimed is:

1. In a modulating system, a source of signals, a polyphase rectifier controlled thereby, a space discharge oscillator supplied with energy from said rectifier, and means comprising a divided resistance and variable condensers in shunt to respective portions of said resistance for eliminating ripples in the rectified current.

2. In a modulating system, a rectifier comprising pluralities of three-electrode electron discharge tubes connected to respective phases of a source of three-phase alternating current, a source of signals, means for impressing signal potentials upon the grid electrodes of said tubes, whereby signal modulated energy is produced in the output circuit thereof, an oscillator supplied with said energy, and means interposed between said rectifier and said oscillator for suppressing variations of current of ripple frequency flowing therethrough, and additional means arranged to superimpose ripple variations upon'said signal potentials, said means comprising a resistance shunted by a plurality of variable condensers connected in series.

3. In a rectifying system, a plurality of three-electrode space discharge tubes, means for heating individually the filaments of pairs of said tubes in parallel, means for adjusting the value of heating currents in said pairs of tubes, whereby a balance of the circuits connected thereto is maintained, means for supplying polyphase current to circuits connected between the plate and filament of said tubes, said means comprising transformers having their primary windings star connected, and means connected in series with a source of signal variations comprising a resistance shunted by a plurality of condensers for substantially eliminating ripple variations in the rectified current.

4. In a modulating system means for rectifying polyphase electric current, said means comprising a plurality of space discharge tubes, haying an input circuit and an output circuit, a source of signal variations connected to said input circuit and reactive means in series therewith to impress ripple potentials on said input circuit, said reactive means being adjustable to vary the amplitude of said ripple potentials whereby ripple currents in said output circuit may be eliminated.

5. In a modulating system a space dismeanscomprising a variable condenser con- -charge rectifier an output circuit including nected in common to said input and output an anode of said rectifier and an input circircuits for eliminating ripples in the rec- 10 cuit including a control electrode of said tified current.

rectifier, a source of polyphase current con- In witness whereof, I hereunto subscribe nected in said output circuit, a source of my name this 13 day o'fDec. A. 1)., 1923.- signals connected in said input circuit, and J. PETER SOHAFER. 

